/*
 * libid3tag - ID3 tag manipulation library
 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id: util.c,v 1.9 2004/01/23 09:41:32 rob Exp $
 */

# ifdef HAVE_CONFIG_H
#  include "config.h"
# endif

# include "global.h"

# include <stdlib.h>
# include <zlib.h>

# include "id3tag.h"
# include "util.h"

/*
 * NAME:    util->unsynchronise()
 * DESCRIPTION: perform (in-place) unsynchronisation
 */
id3_length_t id3_util_unsynchronise(id3_byte_t *data, id3_length_t length)
{
    id3_length_t     bytes = 0, count;
    id3_byte_t       *end  = data + length;
    id3_byte_t const *ptr;

    if (length == 0)
        return 0;

    for (ptr = data; ptr < end - 1; ++ptr)
    {
        if (ptr[0] == 0xff && (ptr[1] == 0x00 || (ptr[1] & 0xe0) == 0xe0))
            ++bytes;
    }

    if (bytes)
    {
        ptr  = end;
        end += bytes;

        *--end = *--ptr;

        for (count = bytes; count; *--end = *--ptr)
        {
            if (ptr[-1] == 0xff && (ptr[0] == 0x00 || (ptr[0] & 0xe0) == 0xe0))
            {
                *--end = 0x00;
                --count;
            }
        }
    }

    return length + bytes;
}

/*
 * NAME:    util->deunsynchronise()
 * DESCRIPTION: undo unsynchronisation (in-place)
 */
id3_length_t id3_util_deunsynchronise(id3_byte_t *data, id3_length_t length)
{
    id3_byte_t const *old, *end = data + length;
    id3_byte_t       *new;

    if (length == 0)
        return 0;

    for (old = new = data; old < end - 1; ++old)
    {
        *new++ = *old;
        if (old[0] == 0xff && old[1] == 0x00)
            ++old;
    }

    *new++ = *old;

    return new - data;
}

/*
 * NAME:    util->compress()
 * DESCRIPTION: perform zlib deflate method compression
 */
id3_byte_t *id3_util_compress(id3_byte_t const *data, id3_length_t length,
                              id3_length_t *newlength)
{
    id3_byte_t *compressed;

    *newlength  = length + 12;
    *newlength += *newlength / 1000;

    compressed = malloc(*newlength);
    if (compressed)
    {
        if (compress2(compressed, newlength, data, length,
                      Z_BEST_COMPRESSION) != Z_OK ||
            *newlength >= length)
        {
            free(compressed);
            compressed = 0;
        }
        else
        {
            id3_byte_t *resized;

            resized = realloc(compressed, *newlength ? *newlength : 1);
            if (resized)
                compressed = resized;
        }
    }

    return compressed;
}

/*
 * NAME:    util->decompress()
 * DESCRIPTION: undo zlib deflate method compression
 */
id3_byte_t *id3_util_decompress(id3_byte_t const *data, id3_length_t length,
                                id3_length_t newlength)
{
    id3_byte_t *decompressed;

    decompressed = malloc(newlength ? newlength : 1);
    if (decompressed)
    {
        id3_length_t size;

        size = newlength;

        if (uncompress(decompressed, &size, data, length) != Z_OK ||
            size != newlength)
        {
            free(decompressed);
            decompressed = 0;
        }
    }

    return decompressed;
}
